Carrier signaling- system



Dec. 8, 1925. 1,565,155

J. S. JAMMER CARRIER SIGNALING SYSTEM Filed Sept. 20, 1923 5Sheets-Sheet 1 Mg m E 3% 10 CS 2 r C E P M Q Q m E g D Q M i. E M

' L L m m Wye/71hr:

Jacob $.J0mmer.

' Dec. 8, 1925. 1,565,155

J. S. JAMMER CARRIER SIGNALING SYSTEM Filed t. 20. 1923 5 Sheets Sheet 3m n //71/e/7/0/": Jami 3 Jam/11 er.

Dec 8, 1925. 1,565,155

J. 5. JAMMER CARRIER S IGNALING SYSTEM Filed Sept. 20, 1923 5 Sheets-She'et 4.

W i f Q 1 Myer? far:

Jacob S. Jammer by iu Affj/ Dec. 8 1925- 1,565,155

.1. S5. JAMMER 4 CARRIER SIGNALING SYSTEM I I Fi d s m zp. 1923 I I 5Sheets-Sheet 5 J0c0b S. Jam/77 er b M Af/j/ Patented Dec. 8, 1925.

UNHTED STATES PATENT ()FFICE.

JACOB S. JAMMER, OZ NEW." YORK, N. Y.. ASSIGNOR TO VIESTERN ELECTRICCOMPANY,

INCORPORATED, OF NEW YURI". N.

Y., A CORPORATION OF NEW YORK.

CARRIER SIGNALING SYSTEM.

Application filed September T at whom it may concern Be it known that I,Jaoor. S. JAJIIMIlih, a citizen of the United States of America.residing at New York city, in the county of New York and State of NewYork, have invented certain new and useful Improvements in CarrierSignaling Systems of which the following is a full, clear, concise, andexact description.

This invention relates to a carrier signaling system.

Multiplex carrier telephone and carrier telegraph systems as heretoforeemployed extend between terminal stations from which radiate lowfrequency lines which are either permanently connected, one to each ofthe carrier channels with a multiplex system or any of which may betemporarily connected to any one of the carrier channels by theoperators at the respective terminal stations.

In some multiplex systems where the low frequency lines are permanentlycoupled to the carrier channels of the multiplex system, the lowfrequency lines extend to other stations which are geographicallyseparated.

For example, a multiplex carrier telephone system between Chicago,Illinois, and Harrisburg, Pennsylvania, has permanently coupled to thechannels thereof low frequency lines extending from l'larrisburg to NewYork and Vashington. Frequently, when all of the usual channels toeither point are busy, it is desired to obtain another channel to one orthe other of said points.

In accordance with the present practice this is accomplished by calling.say, the New York operator who connects to the Chicago-New York channel.a low frequency line extending from New York to Vashington. Thispractice is not only cumbersome but time consuming and utilizes lineswhich should be available for other service. It is, therefore. desirablethat in case, for example, the usual Chicagolvashington channels arebusy, the Chicago operator be able to establish another channel betweenChicago and lVashington without the necessity of going through thestation at New York. This represents. of course, but one of manysituations in which it would be desirable to control the establishmentof a connection from a distance. over a desired carrier channel.

One of the objects of this invention, therefore, is to provide amultiplex carrier signaling system wherein any one of a plurality of lowfrequency lines radiating from one multiplex terminal station may beselected and coupled to a channel of the multiplex system under controlof the other multiplex terminal station.

Other objects and features of the invention relate to the arrangementsfor selecting the desired radiating low frequency line and the properbalancing network therefor, to the signaling and busy test arrangementsassociated with the system.

lVhile the invention is being disclosed as applied to a multiplexcarrier telephone sys tern, it will be understood that it may be appliedto a multiplex carrier telegraph or other signaling systel'u.

In the drawings Figs. 1 and 2 when placed end to end in the order named,show a multiplex carrier telephone system and low frequency linesradiating from one of the terminal stations, either of two of which maybe selected and coupled to a channel of the system.

Figs. 2-3, t and 5 when placed end to end in the order named, show amultiplex carrier telephone system similar to that of Figs. 1 and 2 butwherein a call may be initiated from either end.

The multiplex carrier telephone system of Figs. 1 and 2 comprises. ingeneral. a high frequency main line ML extending between terminalstations X and Y. The apparatus located at station X is shown to theright of the dotted line in It while the apparatus located at station Yis shown to the left and below the dotted line in Fig. 2. The main lineML terminates at station X in a plurality of transmitting and receivingbranches T0,. T0 and TC... and R0,, R0 and R0 and at station Y insimilar transmitting and receiving branches.

Different carrier frequencies are employed for the different channels ofthe system.

The frequencies employed for transmission in one direction are comprisedwithin an entirely different range from those employed for transmissionin the opposite direction.

The transmitting branches are similar so a description of one willsullice.

Transmitting branch T0 includes a of the modulator M to which carriercurrent of the frequency assigned to the channel is supplied from thesource 0 and a band filter TBF The modulator M may be of any well knowntype, such, for example, as the elec tronic valve modulator disclosed inFig. 412 of the article entitled Carrier current telephony andtelegraphy by Colpitts and Blackwell, published in the transactions ofAmerican Institute of Electrical Engineers, volume 40, 1921.

The filter TBF is of the type disclosed in the U. S. patent to Campbell,1,227,113, May 22, 1917. It is designed to pass currents of the carrierfrequency and of the frequen cies within either the upper or lower sideband thereof and to suppress currents of all other frequencies.

The receiving branches are similar so that a description of one willsuffice. v

The receiving branch RC includes a band filter RBF an amplifier A ademodulator DM and a low pass filter LPF The band filter REF is of thetype disclosed in the Campbell patent supra and is designed to passcurrents of the carrier frequency assigned to this channel and of thefrequencies within the same side band as is transmitted by filter TBlFand to suppress currents of all other frequencies.

The amplifier A, and the demodulator DM may be of any well known type.such, for example, as those disclosed in Fig. 412 Colpitts and Blackwellarticle, supra.

The low pass filter LPF is of the type disclosed in the Campbell patentand is de signed to pass currents of frequencies below the upper limitof the voice range of frequencies and to suppress currents of higherfrequencies.

Each pair of transmitting and receiving branches are similarly connectedto a low frequency circuit. For example. the associated trai'ismittingand receiving branches TU and RC, are coupled to and conjugately relatedwith respect to a low frequency circuit O by means of a three windingtransformer 1 and a lnilancine artificial line or network N,.

The low frequency circuits C and (I, coupled to transmitting andreceiving branches of the multiple); system at the sta tion X, mayextend to and terminate in jacks at a switchboard in the usual manner.This switchboard may be located at the station X, or, at a distantstation.

Likewise, each of the associated receiv ing and transmitting branches atstation Y may be similarly connected to low frequency circuits. The lowfrequency circuits C and C are low frequency lines permanently connectedto channels l o. 2 and No. 3

respectively. Line C extends to one disif muse lines have substantiallydifferent electrical chararten istics conmensation therefor may i=cci'i'ccted in any desired manner, such for example as by employingditl'erent balancing networks as will be described in connection withthe system of lligs. 3, l and The low frequency circuit C, terminates inopen contacts of two relays 2 and 3 so that, upon the operation ofeither relay. the

low fret uenc i circuit C mat be ex aidl ed to the terminals of ack J,or J depending upon which relay operated.

N rmally carrier (urrent of the frequency assigned to chaimel No. l andof the upper magnitude, as explained below is flowing therethrough fromstation K to station Y. This current is rectified by the rectifier Rassociated with receiving? branch R C,. The result-in; rectil'icdcurrent flows through relay t. causing it to hold its armature ininid-positimi between the two contacts associated therewith. Themagnitude of this curl. t is controlled by a resistance 5 normallybride-god oss the output of modulator through the center, of relay 6which is normally cneru'ized.

telay controls selecting and coupliiuz; means comprising relays which seect the desired low frequency line and connect the same to the lowfrequency circu ts C' The low frequency lines subject to selection arelines L and la the former ortcndingr to New York, for examp e. and thelatter to Washington. Each of these lines iiGYllii nates in a jack (i(only one of which is shown) which has associated therewith nnalreceiving n'ieans.

The operator at the station who-re the jacks in Fig. terminate. desiringto ostablish a connection to l l ashinu'ton by way of the high frequencychannel with which either of the low frcquencr lines and B, may beassociated, inserts the pine; P of cord circuit CC into jack J Relay 3thereupon operates connecting the low 'lrmuenry (in cuit G, to the tipand rinp' termina s of the jack and operating busy na s lit? associatedwith the. iacks. the actuation of ringing; key iirircsses a source oflow frequency si ialin; ('1, "went onto relay 16 and cans s theoperation thereof. The

relay 6 -which removes resi,

lli

bridged relation to the output of modulator M -rs a result of thisaction the r tutle of the carrier it transmiterl through the channel iseased and the amount of rectified current throinrh relax l increases.Relay -i.- thereupon closes left-hand contact causing the operation ofrelays T and Relay t locks up it a contact thereof and the closed cont:relay 9. The operation of relay 53 selects the low frequency line i andconnects the same to the low it'requeiicp' circuit A busy tone fromsource Bi normally connected to the low freipicm-y lines is discennectedfrom line L, by the operation of relay h.

The operation of relay l causes the eucr-- gization of relay it) whichconnects a source of signaling current 1t to the selected low frequencyline i causing the operation of relay 1) associated with jack 3. Theoperation of rel 12 lights signal lamp 1 3 and energizes r l4- u'hichlorlrs up through its contact and the contact of relay 1%.

Upon the restoration of the ringing key .RK to its normal position.relay 16 releases and relay 6 operates, again bridging resistance 5across the output of modulator M In response thereto relay 4 allows itsarmature to return to the mid-position between the contacts associatedtherewith whereupon relays 7 and 10 release. Ringing current 11 is.therefore. disconnected from the line L which is then connected throughthe contacts of relays 8 and 10 to the line windings of thethree-winding transformer which in turn couples the low frequency line Lto the associated transmitting and receiving branches T C and R of themultiplex system.

The operator at the distant end of the low frequency line L uponobserving the lighted condition of the signal lamp 13 may insert theplug of a cord circuit, similar to that shown in Fig. 1. into the jack Jto answer the call. Relay 15 thereupon operates. opening the lockingcircuit (if-relay 14 which releases. extinguishing the lamp 13. Theoperator at the distant station associated with low frequency line T11may then communicate with the operator at the other station and receiveinstructions for completing the de ired connection. after theestablishment of which. conversation may take place in the oroinarymanner usual to multiplex carrier telephone systems.

At the conclusion of the conversation, the operators withdraw the plugsfrom the jacks, whereupon relays 3 and 15 return to their normalcondition. Relay 8, however, remains locked up so that the low frequencyline L remains coupled to the transmitting and receiving branches T Cand B C of the channel of the multiplex system.

Should the operator now desire to establish connection over the lowfrequency line L the plug P is inserted in the jack J ltelay 2 thereuponoperates, connecting the low frequency circuit C through to the tip andring terminals of the jack J and operating the busy signals BS. Theactuation of ringing key 11K operates relay 16 which releases relay 1?.Relay 17 thereupon closes its contact which places a short-circuitacross the output of the modulator M and reduces to nil the magnitude ofcarrier current transmitted through the channel. The mag nitude of therectified current through relay 4; is, therefore, reduced therebyallowing the armature of the relay to close its right-hand contact.Relays 1S and 9 then operate. Relay 18 locks up through one of itscontacts and the closed contact of relay 7. The operation of relay 9opens the locking circuit of relay 8 which thereupon disconnects lowfrequency line L from circuit C Relay 18, in operating, connects lowfrequency line L to the low frequency circuit C Relay 9 in closing itsfront contact, energizes relay 10 which connects ringing current fromthe source 11 to the low frequency line L. and operates the ringingresponse relay associated with the jack at the distant end thereof,whereupon the signal lamp thereat is lighted. The restoration of theringing key to normal position releases relay 16, energizes relays 17and 4 and deenergizes relays 9 and 10.

The multiplex carrier telephone system of Figs. 3, 4 and 5 is similar tothat of Figs. 1 and 2 in that it comprises a high frequency main line MLterminating at two geographically separated terminal stations W and E ina plurality of transmitting and receiving branches which are associatedin pairs, each pair of which may be coupled to a low frequency circuitor line.

At each terminal, the transmitting and receiving branches are coupled tothe main.

line Mli through a three-winding transformer T, one winding of which isin series with the main line. The second winding is connected to theband filters of the transmitting branches and the third winding isconnected to the receiving branches.

This system, as illustrated, has three channels. Two of these channelsNo. 2 and No. are coupled in the usual manner through three-windingtransformers to low frequency lines EFL and IJFIJ extending from thetermina station and lines LFTF and Fifi extending from station E.

Different carrier frequencies are employed for the different channels ofthe system. The frequencies employed for transmission in one directionare comprised within an entirely different range from those employed fortransmission in the opposite direction.

llach end of channels No. 2 and No. 3 is equipped with means wherebysignals incoming over the low frequency line may be translated intosignals outgoing over the high. frequency line and for translating thesignals incoming over the high frequency line into signals outgoing overthe low frequency line. Since this equipment for each end of the twochannels is alike, it is shown in detail in connection with only onechannel and at one ei'ad thereof only.

This signaling" transmitting equipment may he described in connectionwith the operation. Thus, low frequency signaling;- current ineoinin tothe multiple; terminal station over low frequency line LFL operatesrelay thereby causing the release of relays 2G and 27. The resultantclosure of the contact of relay 2? short-circuits the output circuit ofthe modulator M thereby preventing the flow of carrier current of thefrequency assigned to this channel over the main line. ll heu a ringing;signal is incoming over the main line. as indicated by the absence ofcarrier current therefrom relay 28 in the output circuit of rectifier llreleases causing the energization of relay 99 which thereupon closes itscontacts. The 010- sure of the right-hand contact short-circuits thellllClDOliltSll'lf the line windings of the hybrid coil therebypreventing singing during the ringing operation. The closure of theleft-hand contact operates relay 30 which connects a source of ringingcurrent 31 to the low frequency line LFL Channel. l lo. 1 of themultiplex carrier telephone system illustrated in Figs. 3, iaud 5 hasassociated therewith apparatus and circuits so organized that any one 0tlive low frequency circuits four outgoing and one incoming, may becoupled to the carrier channel at the terminal station W. At theterminal station E there is provided apparatus controlled from terminalstation ll for selectinp any one ot four outgoing); low frequency lines,applying low frequency ringing signaling current to the selected lowfrequency liiio, applying a busy tone to a non-selected low frequencyline, selecting: and connecting the proper balancing network to theselected low frequency line and finally connecting the selected lowfrequency line and its balancing); network to channel No. l. Theselection is effected by shifting the frequency of. the carrier currenttransmitted over the main line ML and selectively operating; at thedistant terminal receiving relays associated With rectifiers coupled tothe channel through selective circuits.

The operator at terminal station W des ring to establish connection byway of channel No. over the low frequency line All extending: fromstation E to a distant station, may insert the plu o a cord circuit,similar to that shown in s 1 into jack A thereby causing; the operationof relay 32. Relay operates lousy signals BS associated with each of thejacks A to E inclusive and also operates relay Relay 33 connects the tipand ring terminals of jack A to the line windings of the three-windingtransformer 1. Relay 3% also causes the operation of relay ill overcircuit including ground connection which thereupon closes the filamentcircuit of the electronic ralre of oscillator Flt) which renders theoscillator active in the generation of oscillations of the frequencyassigned to channel No. l for transmission over the main line fi nustation il to station E. Carrier current of the fl'fiiltlcllty generatedby oscillator SO and tinnsinitted orer the main lino hill is selected bythe tuned circuit TC and impressed upon the rectifier ll. The resul antrectified current flowing in the output circuit of the rectifierenergizes relay 35 whereupon relay releases and relay 8? 0pcrates.llelay 37, in operating, closes the filament circuits of rectifiers All.BR, CR and DR.

After the insertion of the plug in the ack A, the ringing;- key of theassociated cord circuit is actuated causing the operation of relay 38.The operation of relay 3% causes the energization of relay 39 whichconnects condenser 40 in parallel with the condenser of the frequencydetermining circuit associated with the oscillator, thus changing the i?.quency of the current generated thereby. The oscillator now generatesand tnnsmits over the main line current of different frequency which isselected by the tuned circuit Afltl and impressed upon the rectifierAll. The resultant rectified current in the output circuit of theretifier All causes the operation of relay l1. Relays l2 and 4:3thereupon operate. l-lelay 4-2 selects lou frequency line All, andcauses the operation of relay (31 which short circuits a winding oftransformer 4-4: to prevent singing during the ringing operation. At thetime of the cluuine in frequency of the current generated by theoscillator. relay35 releases and relay 36 operates. Relay illbeinga slowrelease relay holds up until relay 43 operates and su mlies a ground forcom )letin the lockino' a. t tn a circuit of relay 37. Relay 43, inoperating, locks up over a circuit including one of its contacts and thecontact of relay 36. The operation of relay 4? also causes the operationof relay All which connects in series with the line windings of thethree-Winding transformer all a balancing; network NA to balance theselected low frequency line All.

The operation of relay 4.3 also causes the operation of relays 45 58 62and 63. litelay 4-5 connects a source of ringing current 4-6 to theselected low frequency line AL. Relays 58 62 and 63 connect a busy tonefrom source BT to the non-selected low frequency lines BL. Cl] and DL.The distant end of the low frequency line AL is teriniated in a jacksimilar to jack J shown in ltlll Fig. 2 and has associated therewithsimilar signal receiving apparatus so that in response to the connectionof ringin current from source to the selected low frequency line All,the signal lamp at the distant end thereof is lighted.

Upon restoration of the ringing key to normal position, relay 38releases thereby releasing relay 39 which shifts the frequency of thecurrent generated by the oscillator back to normal. Relay 41 thereuponreleases and relay operates. Upon the operation of relay 35, relay 36releases but relay 36 is slow to release so that a ground is substitutedat a front contact of relay 45 before being removed at the contact ofrelay 36.. whereby relays 43, AN, 45, 58, 62 and 63 remain locked up.Relay 42, however, controlled through a contact of relay 41 releasesthereby disconnecting ringing current from the low frequency line AL andconnecting this line through to the three-wind ing transformer 44. Relay61 releases when relay 42 releases.

he operator at the distant end of the selected and connected lowfrequency line AL observing the lighted condition of the lamp associatedtherewith, may connect to the jack the plug of a cord circuit similar tothat shown in Fig. 1 and communicate with the operator at the initiatingterminal to receive instructions as to the number of the line to whichconnection is desired. Since the oscillator SO and the modulator M areactive normally, they are in readiness to transmit the return speechfrom station E to station TV as soon as the operator at the distantstation on line AL begins to talk.

After the completion of the connection between the calling and calledparties conycrsation may ensue at the conclusion of which the operatorat station W and at the distant end of the low frequency line AL maywithdraw the plugs from the jacks to restore the apparatus of the systemto normal condition. Then the plug at station is withdrawn from jack A,relays 32 and 34 release, thereby disabling the oscillator SO. Since nocurrent is now being transmitted by the oscillator SO, relay 35 releasesand relay 36 operates. Between the time of the opening of a contact ofrelay-35 and the closure of the contact of relay 36, relay 43 releaseswhereupon relay 37 releases opening the filament circuit of therectifiers AR, BR, CR and DR. The release of relay 43 also causes therelease of relays AN, 45, 58, 62 and 63. Since relay 37 is held up untilthe operator at station XV withdraws the plug of her cord circuit intaking down the connection, the rectifiers AR, BR, etc. are held inreadiness to respond in case of a recall by the operator at station V.This can be done by merely actuating the ringing key in the operatorscord circuit at station W, without having first to withdraw the plug.

The oscillator SO furnishes current of the normal frequency when none ofthe condensers 40, 40", 40 or 40 is connected in parallel with thecondenser of the frequency determining circuit. This normal frequency isthe carrier frequency assigned to channel No. l for transmission fromwest to east. An oscillator S0 at the station E furnishes carriercurrent of the frequency assigned to channel No. 1 for transmission fromeast to west. This oscillator, SO, as stated, is normally operative sothat current of the frequency supplied thereby is normally flowing overthe main line ML and this current is selected by the receiving bandfilter RBI? passes tnrough the demodulator DM the amplifier A and thehigh pass filter HPF and is delivered into the input circuit ofrectifier R Relay 47 is, therefore, energized by rectified current inthe output circuit of the rectifier and remains energized so long ascarrier current is being transmitted over the main line from theoscillator SO.

Should a call originate at the distant end of the low frequency line AL,the plug of the cord circuit thereat is inserted into the jack and theringing key associated with the cord circuit is actuated. Relay 48responds to the ringing current and in responding causes the operationof relays 43, AN, 45 and 49. Relay 43 locks up over a circuitincludingthe contact of energized relay 36 and also maintains relays AN and 45 inlocked up condition. The operation of relay 43 causes the operation ofrelays 58, 62 and 63 which connect a busy tone into low frequency linesBL, CL and DL. The operation of relay 49 short-circuits the output ofmodulator M thereby stopping the transmission of carrier current fromoscillator SO to the main line. Relay 47 in the output circuit ofrectifier R therefore releases and causes the operation of relay 50 andthe lighting of signal lamp 51. Relay 50 looks up through the closedcontact of relay 52 and maintains the lamp in a lighted condition.

Upon the restoration of the ringing key to normal position, relay 48releases thereby causing the release of relay 49 which, in turn, allowsrelay 47 to operate.

The operator at station V observing the lighted condition of lamp 51inserts into the answering jack E, the plug of the cord circuit similarto that shown in Fig. 1 whereupon relay 52 operates opening the lockingcircuit of relay 50 and extinguishing lamp 51. The busy signals BSassociated with the calling jacks A, B, C and D and the answering jackE, are operated upon the energization of relay 52. The operation ofrelay 52 also causes the operation of relay 34 which relay 3? and tofurnish a ground for the locking circuit of relay 43 which ground issubstituted :tor that contact of relay 3o. lay 3t} releases upon theoperation 0'? relay m4.

rnished through the but being slow to release, this contact does notopen until utter the closure of the contacts of i 85. 'ihus the lockingcircuit of rela 'ntained.

i l-it the conclusion of the cr ation, the

pin -s are Withdrawn train the apparatus is restored to noru'ialcondition in the manner previously dose.

l desire "5 channel he plus jack B the op iflhould the opera tor at st:-to establish a connection by N0. 1 to the low trequency line El. t ofthe cord circuit is inserted in the whereupon relay 52% operates,causing eration of the busy signals and relay o l. llelay connects thetip and ring tel-ininals of jack B to the line windings ot transformer 1and causes the operation of relay 3% which starts the oscillator StilThe oscillator SO generates and transi'nits over the line carrier currewhich is selected by the high pass filter liPF and the tuned circuit TU.Relays 35 and 3'? operate and relay releases as before.

The ope 'ator actuates the ringing ltcy of the cord circuit Where iponrelay 55 r sponds, czrusinp, the operation of relay 56 which connectscondenser 40" in parellel with the condenser of the oscillator quencydetermining circuit. The frequency oi the current gene *atcd by theoscillator is thcreliy shifted and tunei'l circuit C lects this shittcdti .c ucncy current and recti tier rectilies the same. The resultantroctiiicd current operates relay 5? which :auses the operation or renys5e and 59. ltclay 58 selects low frequency line BL. and auses theoperation of relay ()1. Relay 59 loci-Is up over a circuit 'inchulin thecontact of relay Which now o ted. ay 59 causes the operation ct re '2 l,42, 62 and ('33. All of these rela now locked up, due to the fact thatrelay is locked up. Relay 60 connects ringing curi nt to the selectedlow irctpiency line Pill which lights the si nal lanip at the other end.Relay Bil con nects balancing network ell in series with the linewindings ott transtornier 4: 1 to halance the selected low frequencyline BL. liel: I 62 and connect a source of lousy tone .l to thenon-selected low frequency lines AL CL and Dill.

Upon restoration of the ringing key to normal position, relays 55 and 56release. The frequency of the current generated by the oscillator S0 isthereby shifted hack to normal so that in response thereto relay 5'?release" and relay 35 operates. Relays 58 and 61 release on the releaseoil relay but relay and those relays dependent thereon remain operatedbecause a ground tor its locking circuit established at the contact ofrelay hetore being removed at the contact oil" slow release relayFurther extension ot the connection may now be made in the mannerpreviously described utter which conversation may ensue. it the couchsion oi conversation, the plug is Withdrawn and the apparaus restored tonorn'ial condition as in the manner previously described.

frlhould the operator at station l f insert the plug into yicl; C. thelow frequency line "ll will he select on. tor. upon the insertion of thepin relay (it operates causing the opi? relay (35. which. in turn.operates 1nd starts the oscill tor SO. lieand 37 then operate and relay36 rein response to the actuation of the lzey ot the connected cordcircuit. operates causing the operation of ay which connects condenser40 in the queue; dctcri'i'iininp; circuit of the oscil- The "frequencyot the oscillator is thus shitte l. Current out the shifted trequency isselected iy ed circuit ETC and rectified by rectifier is and theresultant recti 'ed nt operates relay 68, Whereupon 1' and t? opera-itChe operaselects low "requency line 1 Relay 89, in op tion of re.

and operates elay (5i.

i crating, loclzs up in the manner described in cor i tl it and operatesres lays 58 and uczun network inc wi 111i. balance the selected lounelay4O (OHUGCL ringselected low tlrequcucy tic '. 't 11- the ringing hey tonormal positioin relays (32. (ll. ant. 8 relea-isei relay 35 operatesand rcday 3") releases.

t be selected by "he ul' it our t ot the cord circui into The insc 'onor": the p ug iito the :1 uses the operation of relay it which. ii to.operates relay T2. Relay operat. lav B-lto start the oscillator. ll'cla:y 35' and iii t'unction a. before descr he actuation of the ringingkey 1. ot the connected cord cir "uit causes the re IOl lay Tl. Relays63 and thereupon opcrate. Reta 63 selects the low fre iiency line DL andoperates relay til. llelay T5, in operating, causes the operation ofrelays DE, 7c, 42, 5S and $2. Relay DN connects balancing network ND incircuit with the line windings of transformer it to balance the lowfrequency line Dli. Relay in connects ringing current to the selectedlow fre quency line. Relays 1:2, as and 62 connect the ousv tone sourceto the nonselected low frequency lines. Upon restoration of the ringingkey to normal position, relays 72, 73, ii, 6 3 and 61 release, relay 35operates and relay S6 releases.

Should a call originate at the distant end of low frequency line ISL. CLor Dli, the apparatus associated wit 1 the line on which the calloriginates operates as described in connection with line All to operatethe signal 'eiving apparatus associated with the receiving jack E.

lr'hile only one channel of the multiplex carrier telephone em has beenshown as equipped with apparatus for selecting any one of a plurality oflow frequency lines, signaling thereover and connecting the same to thechannel of the multiple): system, other channels may be similarlyequipped, if desired.

Likewise, in the system of Figs. 1 and other channels of the multiplexcarrier telephone system shown therein may be equipped with selectingmechanism similar to that illustrated in connection with one of thechannels. The channels of the multiple; system (Figs. 1. and notequipped with selcctin mechanism may he equipped with signalingmechanism such as disclosed in detail in connection with the westterminal oi channel IJFL in Fig. 23.

lhe invention set forth herein is. of course. susceptible of variousother embodiments and applications.

I claim:

1. In a carrier wave signaling system, a carrier wave channel, stationsin which said channel terminates, a modulator at one tion, a detector atanother station, a plurality of low-frequency terminal circuits adaptedto be operatively associated with said modulator, a correspondingplurality of low-frequency terminal circuits adapted to be operativelyassociated with said detector, and means controlled in response to thetaltinp; for use of one of the first-mensociating it with the modulatorand for operatively associating one of the secondmentioned plurality ofterminal circuits with the detector.

2. In a signaling system. a two-way carrier wave channel terminating inrespective stations, a modulator and a detector asso ciated with saidchannel at each station, a plurality of low-frequency terminal circuitsat each station arranged for connection with the respective modulatorand detector for repeating into and receiving from the carrier wavechannel, and means controlled in response to the taking for use of oneof the l()\\-fl(]ll0llt}' terminal circuits at one station foroperatively associating it with the modulator and detector of thatstation and for operativcly associating one of the lowfrequency terminalcircuits at the other station with the modulator and detector of thatstation.

3. In a carrier wave transmission system. a carrier wave channelterminating at each end in carrier signaling apparatus, a plurality oflowfrequency terminating circuits adapted for interclumgeable connectionto the carrier signaling apparatus at each terminal of the channel, anoperators cord circuit including a key, means to connect the cordcircuit to any of the terminal circuits at one station, and meanscontrolled in response to the connection of the cord circuit to aparticular one of said terminal circuits and to the actuation of saidkey for connecting to the carrier signaling apparatus at the distant endof the channel the corresponding terminal circuit thereat.

4. In a carrier telephone system, a carrier telephone channel, adetector therefor, a pluralitv of frequency selective circuitsassociated with the detector, a plurality of tele phone lines, meanscontrollable over said channel and including said detector forselectively operating certain of said selective circuits to connect adesired telephone line to said detector, and means for transmittingspeech over said channel and the connected line.

5. In combination, a carrier wave channel including a modulator at oneterminal and a detector at the other terminal, a plurality of terminalcircuits at each terminal adapted for connection respectively to themodulator and to the detector. and means including said channel and oneof the terminal circuits connectible to the modulator for controllingconnection of one of the terminal circuits to the detector, theparticular terminal circuit connected to the detector being dependentupon the terminal circuit over which the control is exercised.

6. In combination, a carrier wave channel, a detector therefor, aplurality of terminal circuits connectible interchangeably to saidtioned terminal circuits for operatively its-detector, and meanscontrolled in response llO to toe fre uency of the were transmitted oversaid channel for selecting and conne ing one of the terminal circuits tothe de tector.

T. It a conni'iunicat" i an, a carrier wave channel terminating at onetation in a detector, a group of lines ada ed for con nectioninterchangealiily with said. detector, means controllable over samlchannel t'or selecting; a line and coni'zecting it to the detector, andmeans to indicate all of the re maining lines of the area asinaccessilfe.

8. in a coininuni ating; system, a carrier Wave channel. a group otlines adapted for operative association interci"oigeahly with saidchannel, and means controllable over any line for opera'ively z.,ociating it with the channel an for iii-{rivaling all of the remaininglines oi the group as inaccessible.

9. In a communicating a carrier Wave channel, inc-ans to'ti 'iyely d1 1z erent over the channel wares frequency characteristics rier Wavecontrolled hy the signals to he sent, a detector tor said cha e W Hin-l, a plurality ot tern'unatinp; lines adapt.. l tor selectiic connectionto said detector, nieans coir trolhhle by Waves transinittec over thechannel and dependent upon the treipiency characte "istics of the vavefor selecting; and connecting; ore of the terminating lines to thedetector, and means operating in response to the 0k 'rier Way tormaintaining the selected line connected during the transn'iission ofsignals.

10. in a signaling system, a carrier Wave channel terminating; in adetector a plurality of terminal circuits adapted for interchangeableconnection to said detector, means controllable over said channel forselecting and connecfing to the detector one of said terminal circuits,:1 id means responsive to the selection of such circuit for applyingsignaling current thereto and indi cating the remaining lines asinaccessible.

ll. In a communicating; system, a carrier Wave channel, terminating in adetector, plurality of ter ninal lines adapted for intcrchangeahleconnection to said channel, a plurality oi? irequency-selective circuitsoperativcl i c ntrol ot the carrier Wave.

in, a con'intruncating; system, a carrier rare channel means to tr;isinit a carrier Wes oi characteristics ware and iii the r-cover, alurality of terminal circuits connectihle to said channel,

means actuated ii. response to receipt of the cari 'icr ware tor enerpother W rig the selective inca s, means to cause the selective means toselect and ccnnect to the channel a deed one of the il circuits, antimeans lining the connection er wave. '21 signaling system, a trezctiyeca'rier transmission chan- I ns to transmit a "\VflVQ ot a particulart'requeuc i'lll'O'tigll said channel contiinioiissly daring signalingperiods, a plurality of terminal circuits, and means for transmittingwaves 01 other frequencies Within the transmissimi frequency range ofsaid channel dirinp' nonslgnalinp; periods or opcrztirely associating aselected one 01": said terminal circuits With said channel.

let. it multiplex carrier telephone system comprising a high frequencymain line extending between two stations Vt and E, a plurality of lowfrequency lines radiating from station E, a plurality of balancing networl-rs, one for each of the low frequency lines, and means at stationcontrolled over the main line from station W tor selecting one of thelow 'treqiiieney lines and its balancing network and coupling the sameto one of the channels of the systen'i.

In witness whereof, it hereunto subscribe n y name this 12th day 0September, A. D.

selective means,

